Fire Lapping?

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Last Post 13 January 2010

CBA Member

nimrod posted this 08 October 2009

I bought a model 12 a while back with the thoughts of shooting some competition with it. The problem is no matter what lead alloy I use or lube or bullet design at the end of the shooting session I seem to have some serious lead left in the bore, probably down toward the chamber area. I am not shooting with much velocity 1600 to 1800 fps and clean every 15 to 20 rounds. I will see some streaks of lead at the muzzle but these clean out fairly easy and it seems that the barrel is clean till I get home and do some serious cleaning. Accuracy falls off after about 50 rounds untill all of the lead is removed. I'm thinking that fire lapping is in order, never done it before and can't find lapping compound locally, where can this be purchased I do have on hand some auto supply store lapping compound, unknown grit, also have been using J-B bore cleaner which hasn't seemed to do much. Also have some Flitz on hand can this be used? Any help would be appreciated

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CBA Member

nimrod posted this 08 October 2009

I had someone ask exactly what I was shooting so will try to clear that up a little. This is a Savage model 12 .308 it has a very short throat. the only two bullets that I can seat and keep the gaschecks in the case neck is the Lyman 311679 and 311299 but both are too small on the bore ride nose. The throat measures .310 just in front of the case and I have no problem sizing the driving bands to fit the throat. I would like to shoot this in the Production class and think that I could have the throat recut which would give me many more options but would like to clear this lead issue up before I open a another can of worms.

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Standard Member

KenK posted this 08 October 2009

I've used the David Tubb jacketed lapping bullets and I've made them myself with 320 grit valve grinding compound and cast bullets.

Both worked fine. I'd probably just buy a box of the Tubb bullets if I just wanted to smooth the bore.

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cityboy posted this 08 October 2009

Have you considered fire polishing? This thread can be found in the TESTING FORUM and was started by Molly.

It works well and is a lot cheaper than the NECO lapping kit or the Tubbs bullets. I fire polished a 2-groove 03-A3 barrel last year with 20 rounds using inexpensive JB bore paste. The load I used was a 150 grain jacketed bullet and 35 grains of IMR3031.

There was still light leading visible at the muzzle. So a couple of months ago I fired 4 more polishing rounds. I don't know if accuracy was improved, but leading is gone.

Jim

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CBA Member

nimrod posted this 09 October 2009

Thanks cityboy that is what I was looking for, I'll try molly's method and see what happens. This rifle actually shoots pretty well just needs a little more load development and be rid of that pesky lead problem. I really think that it starts in the first few inches of the bore and gradually builds up. When I clean after 15 shots at the range the barrel seems to be very slick snd no sign of lead. After a couple of groups fliers start showing up, thats when I usually guit shooting soak the barrel down good with bore cleaner take it home and give it a good cleaning. After a couple days of Kroil, JB, lots of patches I finally get rid of the grey fouling. I'll give the “molly” treatment and report back with good news I hope.

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cityboy posted this 09 October 2009

Nimrod

Please keep us posted on your results.

Jim

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CBA Member

nimrod posted this 19 October 2009

Well I did it, fire lapped with JB six rounds and no more lead. Been to the range twice just to make sure, best shootin to date with this rifle.

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Standard Member

corerf posted this 19 October 2009

I have a Model 12 in 22-250. It shoots VERY well,with J bullets. I have been afraid to do any lapping as I figure at 4k fps it's already getting a lapping or sorts.

Please advise, nimrod on the improvement in groups

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CBA Member

nimrod posted this 20 October 2009

Just my 2 cents worth I would shoot some cast and see what happens your barrel may be just fine. Mine was building up lead on the very edge of the rifling to the point where accuracy would fall off to 2-3 inch groups at 100 yards. You could see this at the muzzle after 10 rounds, didn't seem to matter what alloy or lube was used, after about 3 years of this it's time to do something else {it helps to be stubborn in this game}. Thats when cityboy mentioned the JB method, it made a difference. I can't say that the accuracy improved over what I was getting for my first 2 to 10 shot groups but now I can shoot 50 or more rounds without lead and now can get about to some serious load development. Hope this helps.

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cityboy posted this 20 October 2009

nimrod wrote: Just my 2 cents worth I would shoot some cast and see what happens your barrel may be just fine. Mine was building up lead on the very edge of the rifling to the point where accuracy would fall off to 2-3 inch groups at 100 yards. You could see this at the muzzle after 10 rounds, didn't seem to matter what alloy or lube was used, after about 3 years of this it's time to do something else {it helps to be stubborn in this game}. Thats when cityboy mentioned the JB method, it made a difference. I can't say that the accuracy improved over what I was getting for my first 2 to 10 shot groups but now I can shoot 50 or more rounds without lead and now can get about to some serious load development. Hope this helps.

My initial fire lapping efforts involved 20 rounds. Accuracy seemed to improve. But I still got leading at the muzzle. There may have been more in the bore, but not sure because I lack a bore scope.

Four more fire lapping loads were fired, and leading was no longer visible at the muzzle. Accuracy was about the same. I hope to go out tomorrow and get more info.

Cityboy